Armored cable

ABSTRACT

Armored cable sheath is coded for easy visual identification by applying patterns, e.g., colored patterns, along the length of the cable.

This is a continuation of application Ser. No. 08/139,314, filed Oct.19, 1993, now U.S. Pat No 5,468,914, which is a divisional of Ser. No.07/865,334, filed Apr. 8, 1992, now issued as U.S. Pat. No. 5,350,885.

BACKGROUND OF THE INVENTION

This invention relates to armored cable.

Armored cable typically has a metal sheath enclosing one or moreindividually insulated conductors. The sheath may be formed of ahelically interlocked continuous strip of metal, or of smooth orcorrugated continuous metal tubing.

The National Electrical Code identifies two types of armored cable:"Type MC" and "Type AC". In Type AC, the insulated conductors areindividually wrapped with protective paper, and a bare ground wireextends the length of, and touches the inside wall of the sheath.

In Type MC cable, the insulated conductors are not individually wrappedwith paper; rather they are surrounded as a group with a paper orplastic insulating wrap. The ground wire is one of the individuallyinsulated conductors and, thus, does not touch the inside wall of thesheath. While the internal configurations of Type MC and Type AC armoredcables differ, they have similar external appearances (i.e.,gray-colored metal).

Armored cable is used in wiring homes and commercial buildings. Duringinstallation, appropriate lengths of armored cable are cut from a mainsupply (e.g., a spool, coil, or reel) and pulled or routed through thewalls and ceilings of the building.

Type AC cable must (by regulation) and Type MC cable should (for maximumsafety) maintain an uninterrupted conductive path along the metal sheathfrom one end of the cable to the other. During installation, each end ofthe armored cable is typically connected to a metal terminal box using ametal connector or a plastic connector with a metal pathway thatconnects the armor to the box. The metal of the connector touches boththe exterior of the metal sheath and the terminal box, and thus providesan electrical path from sheath to ground.

Armored cable permits orderly wiring for various applications within abuilding (e.g., fire protection devices, lighting, motors). For example,wires of different sizes serving different applications may be groupedwithin different armored cables. Because the cables typically areinstalled near to each other, and because the cables look identical orsimilar, it is difficult to distinguish the different cables which servedifferent applications. The particular application associated with anarmored cable may or may not be indicated by attaching an identificationtag, stamping a code into the outer surface of the cable's sheath, orwriting (e.g., with an indelible marker) in relatively small printsomewhere on the outer surface of the sheath.

SUMMARY OF THE INVENTION

In general, in one aspect, the invention features an armored cablesheath including a conductive tubular structure having an internalpassage, an outer surface, a first end, and a second end. The internalpassage is sized and configured to enclose one or more conductors. Thetubular structure is made of a material having a first visualappearance. A pattern of visible indicia, of different visual appearancefrom the first visual appearance, is applied on the outer surface and isrepeated along the length of the sheath.

Embodiments of the invention include the following features. The patternhas color, e.g., red, green, blue, or yellow and is repeated at regularintervals along the length of the sheath.

In some embodiments, the conductive tubular structure includes crownsand valleys of a helically wound strip and the pattern leaves exposed asubstantial portion of the outer surface of the crowns, and also leavesexposed a substantial portion of the strip where edges of the stripalong the crowns contact a surface of the strip at the valleys. Thepattern, applied along the length of the strip, may be a continuousstripe narrower than the strip, or may be discontinuous, e.g., asequence of spots. The pattern may be a non-conductive material, and maybe of ink, dye, or paint.

In some embodiments, the tubular structure comprises a cylinder formedfrom a continuous piece of metal tubing, and the pattern is formedrepeatedly along the length of the sheath. The cylinder may have one ormore corrugated outer walls and may have a generally rectangulartransverse cross-sectional configuration.

In general, in other aspects, the invention features a cable includingone or more conductors enclosed within the sheath, and a set of armoredcables having applied patterns of different visual appearance.

In general, in other aspects, the invention features methods of makingan armored cable sheath which include applying visual indicia to theouter surface of a conductive tubular structure or to the strip fromwhich it is made by helical winding.

By looking at the cable, one can easily determine the number ofconductors, type of insulation, and/or type of cable, or the particularapplication. The premarking of various colored designs on the sheathsaves time and reduces errors in handling, installing, inspecting, andmaintaining the armored cable.

Other features and advantages of the invention will become apparent fromthe following description and from the claims.

DESCRIPTION

The drawings are first briefly described.

FIGS. 1 and 3 are perspective views of armored cables installed in abuilding and leading to various areas of the building to be terminatedin distribution boxes serving various circuits.

FIG. 2 is a perspective view of a junction box.

FIG. 4 is a colored drawing of a set of armored cables.

FIG. 5 is a fragmentary plan view of a piece of an armored cable sheathshowing a partial cross-section at each end.

FIG. 6 is a perspective view of a maze of armored cables installed inthe ceiling of a building.

FIG. 7 is a fragmentary plan view of Type MC armored cable sheath,similar to FIG. 5, with insulated wires extending from the sheath.

FIG. 8 is a view of the armored cable sheath in cross-section, takenalong line 8--8 in FIG. 5.

FIG. 9 is an enlarged sectional view of an interlocked connectionbetween overlapping sections of an armored cable sheath.

FIG. 10 is an enlarged, partially sectional view of an armored cablelocked in position by a connector mounted in a terminal box.

FIG. 11 is a fragmentary perspective view of a metal strip used to forman armored cable sheath.

FIG. 12 is a fragmentary perspective view of the metal strip of FIG. 11with a non-conductive coloring material selectively applied to one side.

FIGS. 13, 14, and 15 are fragmentary perspective views of the metalstrip of FIG. 11 with non-conductive material selectively applied invarious configurations.

FIG. 16 is a fragmentary perspective view of a continuous cylinder, witha smooth outer wall, comprising the armored cable sheath.

FIGS. 17 and 18 are fragmentary perspective views of the cylinder ofFIG. 16 with a non-conductive coloring material selectively applied tothe outer wall and insulated wires extending from the sheath.

FIG. 19 is a fragmentary perspective view of a continuous cylinder, withan outer wall having helical corrugations, comprising the armored cablesheath.

FIGS. 20 and 21 are fragmentary perspective views of the cylinder ofFIG. 19 with a non-conductive coloring material applied to the outerwall and insulated wires extending from the sheath.

FIG. 22 is a fragmentary perspective view of a tube, having a generallyrectangular transverse cross-sectional configuration and smooth outerwalls, comprising the armored cable sheath.

FIG. 23 is a fragmentary perspective view of the tube of FIG. 22 with anon-conductive coloring material selectively applied to the outer wallsand insulated wires extending from the sheath.

FIG. 24 is a fragmentary perspective view of a tube, having a generallyrectangular transverse cross-sectional configuration and corrugatedouter walls, comprising the armored cable sheath.

FIG. 25 is a fragmentary perspective view of the tube of FIG. 24 with anon-conductive coloring material applied to the outer walls andinsulated wires extending from the sheath.

FIGS. 26 and 27 are each a schematic process diagram of a manufacturingprocess for making helically-wound color-coded armored cable.

FIGS. 28 and 29 are schematic process diagrams of an off-linemanufacturing process for color-coding armored cable made fromcontinuous tubing.

FIG. 30 is a fragmentary perspective view of the metal strip of FIG. 11with a conductive coloring material applied to one entire side.

FIG. 31 is a fragmentary perspective view of the cylinder of FIG. 16with a conductive coloring material applied to the entire outer wall,and insulated wires extending from the sheath.

FIG. 32 is a fragmentary perspective view of the tube of FIG. 22 with aconductive coloring material applied to entirely cover the outer walls,and insulated wires extending from the sheath.

FIG. 33 is a fragmentary perspective view of the tube of FIG. 24 with aconductive coloring material applied to entirely cover the outer walls,and insulated wires extending from the sheath.

Referring to FIGS. 1, 2, and 3, the color-coded armored cable of theinvention may be installed by routing it along and through the walls andstuds of a building. (Although much of the description refers tocolor-coded cable, it should be understood that non-color patterns mayalso be used for coding the cable.) During installation, the color-codedarmored cable is cut and bent to conform to the features of the buildingand secured in place with fasteners 12. A typical wiring job requiresarmored cable of various types, e.g., one application within thebuilding may require armored cable enclosing relatively few conductorsof relatively large gauge, and another application may require armoredcable which houses a relatively large number of conductors of relativelysmall gauge. The particular application determines the kind of armoredcable used. (Any application permitted under the applicable codes ispossible, e.g., wiring for fire alarm systems, generators, motors,lighting, HVAC systems.) During installation, all armored cablesassociated with the same application or all armored cables of a giventype are selected to have the same color and color pattern on theirsheaths, and (in the case of a given application) are typically, butneed not be, located near each other.

One group of color-coded armored cables 10 may serve a fire alarmsystem, for example. Another group 14 may serve an HVAC system. Stillanother group 18 may serve lighting fixtures. All armored cablesbelonging to a particular group bear the same color or the same patternof markings, for example, red for group 10, blue for group 14, andyellow for group 18. The different colors allow quick and easy visualidentification of all cables for a particular application. This aids ininspecting and tracing the cables after installation, even though therouting of the cables may be disorganized. (Referring to FIG. 6, atypical wiring job utilizing armored cable may include a disorganizedmaze of armored cables 17 installed above ceiling beams 15 and behind awall 16.)

Referring to FIG. 4, a set of four armored cables 30 may include sheathswith blue markings 32, red markings 34, yellow markings 36, and orangemarkings 38 (other colors and patterns of markings could be used). On atypical wiring job the use of a set of color-coded armored cables savestime, improves safety, and reduces error.

The color markings also allow the armored cable to be inventoried andretrieved quickly and accurately. The color markings on the armoredcable are easily seen from a distance. The color markings also mayreduce the chance of a person cutting into either the wrong circuit oran energized circuit during modification or installation work.

Referring to FIG. 5, color-coded armored cable sheath 50 may be ahelically-wound tubular structure having an outer surface 52 and aninner surface 54. (The armored cable sheath has been cut at 56, 58 toallow the inner surface 54 to be seen. ) In some embodiments anon-conductive colored ink 60 colors selective portions of the outersurface 52.

Referring to FIG. 7, a section of Type MC armored cable hasindividually-insulated wires 62 extending through the internal passageof sheath 50. The group of wires 62 is also surrounded by a layer ofinsulation 64 (e.g., a wound strip of thin, protective paper or plastic)which also lies within the internal passage of sheath 50. Thecombination of the armored cable sheath 50 and the enclosed conductorsis referred to as armored cable.

During manufacture of an armored cable sheath, a strip of metal first isformed to produce a contour that includes crowns 66 and troughs 68. Thestrip is then helically wound and interlocked to form a strong, bendablearmored cable sheath.

Referring to FIGS. 8 and 9, when interlocked, the edge 67 of the stripwhich forms one turn makes sufficient electrical contact along its edgelength with the outer surface 69 of the next winding of the sheath (andedge 71 makes sufficient contact with surface 73) to assure a conductivepath along the length of the cable. The electrical contact between eachturn of the strip and the adjacent turn provides a conductive path alongthe sheath from one end of the cable to the other. This conductive pathsupplements the long helical conductive path provided along the surfaceand body length of the metal strip, which also contributes to theconductivity along the length of the cable.

To ensure the integrity of this supplemental conductive path, whennon-conductive colored ink 60 is used, it is selectively applied to theouter surface 52. Because the colored ink 60 is non-conductive, it isnot applied to the edges of the strip which must interlock and makeelectrical contact with the next winding of the sheath. The ink is alsonot applied to portions of the cable sheathing (i.e., the crowns) whichtouch the connectors used to attach the cable to electrical panels orboxes. This assures the conductivity of the electrical path to groundthroughout the circuit.

Referring again to FIG. 5, in some embodiments, the non-conductivecolored ink 60 is selectively applied as a stripe to one side of themetal strip (the side corresponding to the outer surface of the sheath)before the metal strip is helically wound. The stripe of colored ink isnarrower than the width of the metal strip to which it is applied. Insome embodiments, the stripe of colored ink is not centered on the metalstrip but instead is positioned closer to one edge of the metal stripthan the other edge. (Approximately 2 mm of bare metal is maintained onone side of the stripe of colored ink, and about 3 mm of bare metal ismaintained on the other side of the stripe, although the actual figuresare at least partially dependent on the width of the metal strip beingemployed and the desired electrical conductivity.)

Referring to FIG. 10, when the inked metal strip is helically wound toform the sheath, the wider area of bare metal corresponds to the exposed(i.e., bare metal) crowns 66. The bare metal portion of the crowns 66that results from the selective placement of the non-conductive coloredink assures good electrical contact with a connector 19 used to attachthe end of the cable to a metal terminal box 20. In some embodiments,connector 19 includes a metal lock screw 11 attached to a metal lockplate 13 which bears against the armored cable 50 and locks it securelyin place when screw 11 is tightened. The connector 19 thus makeselectrical and mechanical contact with the armored cable 50 via themetal plate 13, the screw 11, and the wall of the connector 19. (Themetal terminal box 20 is in electrical contact with the connector 19,and that the end of the armored cable 50 is capped with a protectivebushing 21.)

Referring to FIG. 11, the metal (e.g., aluminum or steel) strip has twoopposite sides 74, 76, and in some embodiments is about 1 cm wide andabout 0.5 mm thick. Referring to FIG. 12, stripe 78 in the case ofnon-conductive colored ink is selectively applied to one side 74 of themetal strip 72. Continuous strips of bare metal 80, 82 extend lengthwiseon either side of the stripe of colored ink 78. In some embodiments, onecontinuous strip (e.g., strip 80) is about 3 mm wide, and the othercontinuous strip (e.g., strip 82) is about 2 mm wide.

Referring to FIG. 26, during manufacture, metal strip 100 is fed from asupply spool 102 to an inking machine 104 which selectively appliesnon-conductive colored ink to one side (the top side in the figure) ofthe metal strip 100. The inking machine 104 includes an inking roll 106which supplies ink to an etched roll 108 contacting one side of themetal strip. The etched roll 108 applies the to the metal strip as athird roll 110 holds the metal strip against the etched roll 108. Themetal strip exiting the inking machine 104 enters a profile machine 112which forms the inked metal strip into an "S" shape (see thecross-section in FIGS. 5 and 8). Next, the S-shaped, inked metal stripis helically wrapped around one or more conductors 114, provided from asupply spool 116, by a convoluting machine 118. The convoluting machine118 forms the interlocking edges which, among other things, provide thesupplemental electrical continuity (from one end of the sheath to theother) described previously. (The convoluting machine 118 also formsslight indentations 70, as seen in FIGS. 5, 7, and 8, on the innersurface 54 of the sheath.) The helically-wound, color-coded armoredcable 120 exits the convoluting machine 118 as the finished product, andis collected on take-up spool 122.

Other embodiments are within the following claims. For example, thestripe of non-conductive colored ink (FIG. 12) may be centered on themetal strip instead of being positioned closer to one edge of the metalstrip than to the other edge. Also, a metal strip having a differentwidth and/or thickness from the strip 72 of FIG. 11 may be used.

The non-conductive colored ink may be applied in a wide variety ofconfigurations other than a stripe, a few examples being shown aspatterns of squares 84 (FIG. 13), dots 86 (FIG. 14), or Xs 87 (FIG. 15).It is also possible to apply varying or combined patterns to theexterior of the armored cable sheath, e.g., a repetitive sequenceincluding a dot followed by a square. One strategy for applying thepatterns is to assure that regions of bare metal 80, 82 appearfrequently along the length of the strip so that virtually any contactsalong the length of the sheath will be electrically conductive contacts,and so that the crowns 66 on the sheath have bare metal portions formaking adequate electrical contact with the metal connector 19 (FIG.10).

Referring to FIG. 16, the convoluted metal strip could be replaced bycontinuous metal tube 200 having a relatively smooth outer wall (ofappropriate thickness to permit bending) and an internal passage 202.The colored markings are applied to the exterior surface of the tube200. The pattern may be, for example, continuous stripes 204, spacedaround the circumference of tube 200 (FIG. 17) or rows of dots 206 (FIG.18). The main requirement is that bare metal be exposed as necessary toassure that a metal connector attached anywhere along the length of thecable will make electrical contact with the smooth outer wall of tube200.

Referring to FIG. 19, alternatively the armored cable sheath may be acontinuous solid metal tube 210 having an outer wall with helicalcorrugations and an internal passage 212. The corrugations allow thetube 210 to be bent more easily, at greater angles, and into smallerarcs than an uncorrugated tube. Two possible patterns include stripes(FIG. 20) and dots (FIG. 21).

Referring to FIG. 22, the continuous metal tube 220 could have agenerally rectangular transverse cross-sectional configuration andsmooth outer walls 222, 224, 226, 228. Referring to FIG. 23, as oneexample, the ink may be applied in continuous stripes 232 or otherconfigurations suggested in the other figures.

Referring to FIG. 24, the rectangular cross-section tube could havecorrugated outer walls 242, 244, 246, 248. Referring to FIG. 25, the inkmay be applied, as one example, in a pattern of dots 252, or in themanner shown in the other figures.

Regardless of the pattern, it is useful to apply enough colored ink tothe sheath to make the color of the armored cable readily visible from adistance.

In other embodiments the exterior of the cable may be coated with a widevariety of other non-conductive materials other than ink, for example,dye or paint or others. Ultraviolet curing flexographic inks (available,e.g., from QureTech, Inc., Seabrook, N.H.) could be used. Also, ifaluminum is used, the aluminum may be anodized to form non-conductivecolor as part of the metal itself.

Conductive materials such as conductive ink, dye, or paint or otherconductive materials may also be used in place of non-conductivematerials. The conductive materials may be applied in the same mannerdescribed for the non-conductive materials. When conductive coatings areused for color coding, the patterns of coating need not leave as much(or any) bare metal on the exterior of the armored cable sheath. Forexample, referring to FIGS. 30, 31, 32, and 33, a conductive coating 300may cover the entire exterior of a sheath of an armored cable. Also,multiple colors could be used on a cable in a single pattern or acombination of patterns.

Coding of different armored cables could be done by differentiating thepatterns of markings rather than the colors of the markings on the outersurface of the sheath. For example, a red striped pattern could be usedfor one application and a red dotted pattern for another application.The markings need not have any color but could be done in the form ofpatterns. Whatever visual indications are used, they should be easilydistinguishable when viewed from a distance and should appearcontinuously or at frequent intervals along the length of the cable sothat even a short length of cable will be easily identified.

Referring to FIGS. 28 and 29, in forming the color-coded armored cablefrom a continuous tube 88, the continuous tube 88 is laid flat and ahook 89 with a long handle 90 is inserted through the internal passageof the tube. One end of each wire that is to be enclosed by the tube toform the finished armored cable is attached to the hook 89, and thewires are drawn through the tube 88 by use of the handle 90. The tube 88may be, for example, a smooth-walled cylinder (FIG. 16), acorrugated-wall cylinder (FIG. 19), a smooth-walled tube having agenerally rectangular transverse cross-section (FIG. 22), orcorrugated-wall tube having a generally rectangular transversecross-section (FIG. 24).

With the wires extending through the length of the tube 88, the armoredcable 92 (i.e., the tube 88 with the wires inside) is, e.g., rolled ontoa supply spool 91. To color and form the armored cable 92, the cable isfed off the supply spool 91, into an inking machine 93 (similar to theinking machine of FIG. 26), and through a convoluting machine 94. Theconvoluting machine 94 may form, e.g., convolutions, rectangular shapes,or corrugations in the exterior of the color-coded armored cable. Thecolor-coded, convoluted (or shaped) armored cable exits the convolutingmachine and is collected on a take-up spool 95.

The inking machine 93 may be moved (as indicated by arrow 96) to theposition indicated in phantom in FIG. 29. In its alternative position,the inking machine 93 marks the armored cable with colored ink (or dyeor paint, as described previously) after it exits the convolutingmachine 94 but before it is collected on the take-up spool 95.

The continuous tube 88, through which the wires are pulled with hook 89and handle 90, could already have color markings (e.g., in the form ofstripes or dots) on its exterior prior to processing to form thecorrugated armored cable. In this case, the inking machine 93 would notbe used at all in the process of FIG. 29.

If color-coded armored cable having a smooth wall is required, theconvoluting machine 94 would be omitted and only the inking machine 93would be used in the manufacturing process of FIG. 28.

Referring to FIG. 26, the marking of the helically-wound color-codedarmored cable may be done after the sheath is formed by moving (asindicated by arrow 124) the inking machine 104 to the position indicatedin phantom.

Another process of forming the helically-wound color-coded armored cableis to supply metal strip already having a stripe (or some other pattern)of colored ink (or dye or paint) on one side to the profile machine 112.This alternative process would not require an inking machine 104 to beincluded in the process of profiling and convoluting the metal striparound the conductor(s) 114 to form the helically-wound color-codedarmored cable.

Referring to FIG. 27, as an alternative to FIG. 26, during manufacture,one or more conductors 114 may be fed from the supply spool 116 througha rotating machine 103 which rotates the supply of metal strip 100. Themetal strip 100 enters the profile machine 112, which forms the metalstrip into an "S" shape (see the cross-section in FIGS. 5 and 8), andthen passes into the convoluting machine 118 which helically wraps theS-shaped metal strip around the conductor(s) 114 to form the armoredcable. The armored cable enters the inking machine 104 (indicated inphantom) which selectively applies colored ink as described previously.The helically-wound, color-coded armored cable 120 exits the inkingmachine 104 as the finished product, and is collected on take-up spool122. If pre-marked metal strip is provided by the rotating machine 103,the inking machine 104 (indicated in phantom) may be eliminated from themanufacture process of FIG. 27.

Referring to FIGS. 26, 27, and 29, the inking machine could use "inkjet"or paint sprayers to apply the colored material (e.g., ink, dye, orpaint, whether conductive or non-conductive) to the metal strip insteadof using the inking roll and etched roll. Also, a brush-type applicationinstrument could be used in place of the rollers or sprayers. A constantsupply of ink, dye, or paint would be supplied to the brush-typeapplicator during the application process. Dip pans or wipes could alsobe used.

What is claimed is:
 1. An armored cable sheath comprisinga continuousmetal tubular structure having an internal passage, an outer surface, afirst end, and a second end, the internal passage being sized andconfigured to enclose one or more conductors, said tubular structurebeing made of a material having a first visual appearance, the tubularstructure having an outer surface with periodic crowns and valleys alongits length, and a stripe of marking material, of different visualappearance from said first visual appearance, applied on said outersurface, along the length of said sheath.
 2. The cable sheath of claim 1wherein the crowns and valleys form a helical configuration on the outersurface.
 3. The cable sheath of claim 1 wherein the marking material iscolored.
 4. An armored cable sheath comprisinga continuous metal tubularstructure having an internal passage, an outer surface, a first end, anda second end, the internal passage being sized and configured to encloseone or more conductors, said tubular structure being made of a materialhaving a first visual appearance, and a coating of colored markingmaterial, which covers substantially all of the outer surface of thetubular structure in a manner that permits a connector which is to beattached to the outer surface to make a grounding contact with the metalstructure.
 5. An armored cable comprisinga continuous metal tubularstructure having an internal passage, an outer surface, a first end, anda second end, the internal passage being sized and configured to encloseone or more conductors, said tubular structure being made of a materialhaving a first visual appearance, the tubular structure having an outersurface with periodic crowns and valleys along its length, a stripe ofmarking material, of different visual appearance from said first visualappearance, applied on said outer surface, along the length of saidsheath, and conductors within the tubular structure.
 6. An armored cablecomprisinga continuous metal tubular structure having an internalpassage, an outer surface, a first end, and a second end, the internalpassage being sized and configured to enclose one or more conductors,said tubular structure being made of a material having a first visualappearance, a coating of colored marking material, which coverssubstantially all of the outer surface of the tubular structure in amanner that permits a connector which is to be attached to the outersurface to make a grounding contact with the metal structure, andconductors within the tubular structure.